Resource Book on Horticulture Nursery Management

cushion of air maintained at low positive pressure. Single sheets of plastic, wide enough
to span the entire truss from ground to ground, are rolled out the length of the greenhouse
and are attached to the greenhouse along its length at the ground level on both sides or
Quonset greenhouses and in the gutters or gutter-connected greenhouses. The ends the
sheet overlap the greenhouse ends by a few centimeters and it is attached at that point.
The sheet is not attached to the trusses.
Greenhouse Construction Related Aspects
There are multifold considerations in selecting the site for the greenhouse. The
geographical location may be chosen for its optimum climate favorable for plant growth
or proximity to the market. Once the geographical location has been selected, the items to
consider in addition to the above are topography of the land, transportation and present
and future effects of adjacent properties.
Location: The first consideration in establishing a greenhouse is that of location.
Several factors to be considered in this respect,
Room for Expansion: A land larger than the immediate needs should be acquired.
The ultimate size of the range should be predicted. Area should then be added to this
predicted figure to accommodate service buildings, storage and access drives. Doubling
the area covered by greenhouses would constitute a bare minimum. Finally, extra space
should be allotted to cover unforeseen needs. For instance, it may become necessary to
engage in stockpiling of supplies as fostered by short ages of materials, or the future may
call for holding ponds for water effluent from the range in order to reduce the nutrient
content before releasing it into streams or the groundwater table.
The floor area of service buildings required for small firms is equal to about 13
percent of the greenhouse floor area. This requirement diminishes with increasing firm
size to an area equal to 7.5 % of the growing area. On the average, service building are
equal to 10 % of the growing area.
Accessibility of the Site: This is an important aspect for establishment of a
greenhouse. If the proposed site is hilly, it should be anticipated that considerable land
preparation will be required. Access roads to the property will need to be large enough
and surfaced to handle large motor freight equipment. The type of neighboring properties
may have varied effects on the greenhouse business. If it is an industrial area or becomes
one-there could be damage to crops from some kinds of air pollution. The problems that
might develop in the future are a matter of estimation. Greenhouses that were built
outside of cities become surrounded by urban development with increased pressure of
urbanization may develop problems in future.
Available Water: Water is one of the most frequently overlooked commodities in
the establishment of a greenhouse business. Before a site selection, the available water
source should be tested for quality and quantity. There are several cases where green
house located in coastal and riverbed regions have been compelled to move to new
locations to obtain water of suitable water quality. The cost of removing ions such as
sodium, chloride, and bicarbonate is expensive but failure to do so result in plant injury.
Water quantity is equally important since as much as 20 liters is used per square meter of
growing area in a single application. Well water is the desired source since municipal
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